The invention relates to a small diameter fiber optic cable including an uncorrugated armor shielding that maintains flexibility and mechanical strength in the cable.
A first type of conventional cable includes a protective armor shielding disposed about one or more signal-carrying optical fibers in order to protect the fibers while maintaining adequate flexibility in the cable. The armor shielding typically comprises a corrugated metal. However, the use of a corrugated material increases the amount of material necessary to protect a given length of optical fibers and further increases the cable diameter and weight. The corrugated material also requires an additional processing step, thereby increasing the manufacturing time, and further increasing the probability that the metal armoring can be damaged during the corrugation process.
As a second conventional device, optical fibers are armored with a welded steel tube. However, the process for producing the welded tube is very complicated and slow, thereby increasing manufacturing costs. Welded steel tubes have performance advantages, such as better structural integrity. However, welded steel tubes also have attendant disadvantages such as decreased flexibility.
As a third conventional device, a flat (uncorrugated) steel tape becomes bonded to a cable jacket. However, the bonding in such conventional cables does not provide sufficient flexibility to pass industry-based flexing tests. In particular, because the bonding between the jacket and armoring tape cannot be made uniform, local stresses accumulate at areas where bonding forces are weak. Thus, such bonded flat metal tapes introduce an unacceptably high level of localized bending stress in the cable armor.
Applicant""s invention overcomes the above deficiencies. The inventor of the present inventive cable observed that non-corrugated armor tapes could meet necessary industry standards by maintaining the ratio of the armor tube diameter and the thickness of the jacket tube wall for a specified cable diameter within a prescribed range. This ratio permits flexing that comports with industry standards while maintaining adequate cable resistance in compression and tensile tests.